1. Field of the Invention
The present invention relates to a medical image processing device for taking and displaying a medical image of an object of interest in a body cavity and a method for operating a medical image processing device.
2. Description Related to the Prior Art
In diagnosing stomach cancer, it has been recognized that the onset of the stomach cancer is closely related to the presence of Helicobacter pylori (H. pylori). In 1994, WHO (the World Health Organization) announced that the H. pylori is a carcinogen. The eradiation of the H. Pylori infection has been performed to prevent the stomach cancer. After the eradication, whether the eradication has been successful is examined.
Whether a patient is infected or uninfected with the H. pylori is examined by a blood test or by using an endoscope system, which comprises a light source device, an endoscope, and a processor device. In the endoscope system, illumination light is applied from the endoscope to an object of interest (hereinafter simply referred to as the object). Based on RGB image signals, which are obtained by taking the illuminated object with an image sensor of the endoscope, an image of the object is displayed on a monitor. In a case where diffuse redness appears in the image on the monitor, it is diagnosed that there is a high possibility of the presence of the H. pylori and it is likely to cause cancer.
It is known that the presence of the H. pylori correlates with IHb (also referred to as the hemoglobin index, which is represented by a G/R ratio between a G image signal and an R image signal) (see Japanese Patent Laid-Open Publication No. 2003-220019). In this document, the IHb is used as an index for determining whether the eradication of the H. pylori infection has been successful. According to this document, in the case where the IHb is greater than a threshold value “59”, it is diagnosed that the eradiation of the H. pylori infection has not been successful and the H. pylori is still present. In the case where the IHb is less than the threshold value “59”, it is diagnosed that the H. pylori has been eradicated successfully.
As illustrated in FIG. 28, in a feature space formed by the B/G ratio (the vertical axis, the ratio between the B image signal and the G image signal) and the G/R ratio (horizontal axis), the coordinates corresponding to a portion (of the object) uninfected with the H. pylori are distributed in an observation area “A”. The coordinates corresponding to a portion (of the object) infected with the H. pylori are distributed in an observation area “B”. The coordinates corresponding to a portion (of the object) in which the eradication of the H. pylori infection has been successful are distributed in an observation area “C”. In this feature space, the observation areas “A” and “B” are completely apart from each other. In this case, the observation areas “A” and “B” are distinguished from each other based only on the value of the G/R ratio (the horizontal axis), that is, the value of the IHb. On the other hand, the observation area “B” is in proximity to the observation area “C” and they are partly mixed in the feature space, so that it is difficult to distinguish the observation area “B” from the observation area “C” based only on the value of the G/R ratio (the value of the IHb). It is necessary to display images which allow distinction, using a method other than that using the IHb, between the portion infected with the H. pylori infection and the portion in which the eradication of the H. pylori infection has been successful.